Madhya Pradesh police today arrested - and subsequently released -- 30 activists, including Medha Patkar, Yogendra Yadav and Swami Agnivesh, in Ratlam, while they were on their way to Mandsaur to meet families of farmers killed in police firing.

The activists were stopped by the police at the Dhodhar toll plaza in Ratlam district's Jaora town and detained in the circuit house there for about 30 minutes.

"They dispersed after they were released," City SP Deepak Kumar Shukla said.

The police told the activists, among them JNU students' union president Mohit Kumar Pandey and representatives from farmer outfits, that their visit could disturb peace in Mandsaur, where prohibitory orders under CrPc Section 144 are in place, though curfew was lifted yesterday.

"Our arrest is against the law as no written order was shown to us," Yadav, of the political outfit Swaraj India, told reporters after the arrest.

He stressed the group had wanted to meet the families in Mandsaur "peacefully" and wanted to present them with a "letter of tribute" and soil brought from different parts of the country.

"But we were not allowed to go to Mandsaur," he said.

On being stopped from entering neigbouring Mandsaur, the activists sat on a protest on the Mhow-Neemuch Highway, disrupting traffic, the police said.

The activists raised slogans against the government and in support of farmers for about an hour.

The police said the activists were arrested when they insisted on being allowed to enter Mandsaur.

Yadav also demanded that the government waive farmers' loans and give them higher prices for agriculture produce.

He called for a probe into the death of six people who had been killed in the stir. Five died in police firing, and one was allegedly beaten to death.

Patkar said she could not understand how their presence in Mandsaur could disturb the situation.

"We are not going there for any protest or demonstration, we just wanted to meet the deceased farmers' families," she said.

Heavy police force and water cannons were deployed and barricades placed, hours before the activists reached the Dhodhar toll plaza.

The Mandsaur-Neemuch region, about 300 km from state capital Bhopal, became the nerve centre of the storm of farmer distress, as protests over low prices for crops and heavy farm debts started on June 1 and snowballed into a widespread agitation.

In Mandsaur, curfew was imposed after the five farmers were killed in two incidents of police firing during the protest on June 6.